Answer: first number = 30
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Work Shown:
Consecutive numbers follow right after another (eg: 7,8,9,10,...)
x = first number
x+1 = second number
x+2 = third number
x+3 = fourth number
Add up the expressions and set this equal to 126
(x) + (x+1) + (x+2) + (x+3) = 126
x+x+1+x+2+x+3 = 126
(x+x+x+x) + (1+2+3) = 126
4x+6 = 126
4x = 126-6
4x = 120
x = 120/4
x = 30 = first number
x+1 = 30+1 = 31 = second number
x+2 = 30+2 = 32 = third number
x+3 = 30+3 = 33 = fourth number
Check:
30+31+32+33 = 126
Answer is confirmed.